– What “writes” the information on DNA? And how does it adquire that information?
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DNA is a kind of molecule called a polymer, meaning it is a long string made out of repeating subunits. DNA has 4 subunits, called nucleotides. The information stored in DNA is stored in the ordering, or sequence, of these nucleotides. In and of itself, this sequence is meaningless; what makes this stored information and not just a random string of nucleotides is something called the Central Dogma of Biology, which says that DNA is transcribed into RNA, which is then translated into proteins. Proteins our little molecular machines that do all of the things required to keep you alive: they move stuff around, made reactions happen, give your cells structure, flex muscles, etc. Proteins are another kind of polymer made out of 21 different kinds of amino acids (in humans), all combined together is a unique order for each specific protein.
Now, getting back to DNA. Your body ready DNA in three nucleotide chunks called codons; each codon corresponds to a single amino acid. This is how DNA sequence dictates proteins, by encoding for codons which are translated into amino acids. This ordering of amino acids is the information that is stored in DNA.
Now, your other question of how did this information get acquired is a bit of an open question in science. We don’t know how life originated, and we don’t know if we will ever know. Some significant experiments have shown that the conditions that existed in the early days of the planet Earth could have led to the formation of the required molecules just through the natural chemistry taking place at the time. These necessary molecules have also been found on meteorites, demonstrating that they form naturally just as a consequence of complicated chemistry. How did it all come to be? This is a complicated question for us, because currently life requires both DNA and proteins, but you need proteins to make DNA and you need DNA to make proteins! There are a few theories about how this came about, one major one is called the RNA world. It says that RNA actually came first, before either DNA or proteins. RNA is actually able to do everything that both DNA and proteins can do, just not quite as good as they do. So it’s theorized that we started with RNA only, and then evolved DNA and proteins. It’s
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